U.S. Rep. Mark Kirk told several Republican leaders Wednesday he was set to run for Senate, GOP sources told the Daily Herald.

Kirk of Highland Park has been debating a run for Senate or governor for months, but apparently made the final decision as Illinois Attorney General Lisa Madigan announced she was backing away from a run for U.S. Senate or governor in the 2010 election.

Kirk spokesman Eric Elk declined to comment Wednesday on whether or not the congressman had informed GOP brass about an intention to run for Senate.

Kirk's potential bid has been championed by state and national party leaders. They view his voting record in Congress over five two-year terms, siding with the party often but breaking away on environmental and social issues, as a perfect mix to win statewide office in the Democratic state.

He already has an endorsement from former Illinois Gov. Jim Edgar, who led the state in the 1990s.

"He attracts votes in large percentages from both independents and Democrats," Edgar said. "He is the moderate kind of Republican that can win statewide in Illinois."

As Kirk has debated a run for Senate, he raised more than $580,000 this spring and now has more than $1 million to launch his campaign with.

Millions more dollars will likely be needed in a race expected to draw national attention as Republicans hope to cut back a 60-vote supermajority Democratic lead in the Senate.

On the Democratic side, contenders could include Illinois Treasurer Alexi Giannoulias and Merchandise Mart boss Chris Kennedy, both of whom are hoping for support from President Barack Obama. Giannoulias is an Obama friend and U.S. Sen. Ted Kennedy - Chris Kennedy's uncle - was an early and crucial supporter of the Illinois Democrat's presidential ambitions.

Incumbent Roland Burris may also make a run, but he has been under a cloud since his appointment by Rod Blagojevich after his arrest on corruption charges. A U.S. Senate ethics inquiry into Burris' interactions with Blagojevich before that appointment remains ongoing.

Petitions to get on the ballot are set to be circulated next month. The primary is set for February and general election is in November.

In his north suburban 10th District, Kirk fended off two strong challenges from Democrat Dan Seals last year and in 2006, winning by about 3 percentage points each time.

In the campaigns, Kirk highlighted his positions that complement Democrats, including on stem cell research and environmental regulation.

He also played up his military service. As a U.S. Naval Reserve Officer he was deployed briefly to Afghanistan in the winter.

But Kirk's Democratic-leaning votes have often landed him in hot water with some elements of his own party.

Lately he has taken considerable heat for supporting Obama's cap-and-trade policy that will effectively tax carbon dioxide emissions from corporations, like electricity plants.

But Kirk has also been with Republicans on key votes this year. He opposed Obama's stimulus plan, which included tax cuts, and the budget.